Shock strut



Dec. 31, 1940. c. v. JOHNSON SHOCK STRUT original Filed May 19, 1957'v ATTQRNEY.

35 close the ports 30 during the compression stroke of the piston. The upper e'nd of the casing 24 Patented lDec. 31 1 940 PATENT OFFICE Carl -V. Johnson, South Bend, Ind., assigner to Bendix Aviationcorporation, South Bend, Ind., a 'corporation of Delaware c originnapplicauon my .19. 1937, sei-1n No. v 143,456.- Divided and this application August 17, 1939, serial No. 29o,s4s l 3 Ciaims.

This inventionv relates to shock absorbing means, and is illustrated as embodied in a shock strutforan airplane landing gear.

An objectA of the invention is to provide a .simple and 'rugged structure in the strut for yieldingly carrying the load of the plane in taxying, after the shock of landing has been absorbed. Various features of novelty, and the details of an improved construction, will be apparent from the following description of the illustrative'embodiment shown'in the accompanying drawing, in which:

Figure 1 is a vertical sectional view of a shock absorbing strut embodying the invention illustrating the strut in extended position; and

Figure 2 is a vertical sectional view illustrating the same strut in the compressed position.

A preferred embodiment of the invention illustrated in Figures 1 and 2 of the drawing includes a cylindrical `casing IE! having threaded-"in its lower end a diaphragm or support l2 retained against displacement by a weldingbead i4. The

bead also serves to seal the lower end of the casing against leakage; and a metering pin i8 of conventional type is suitably mounted on the support l2 within the casing. The upper end of the casing I has a portion slightly enlarged in diameter as at I8 providing apacking chamber and an annular shoulder 22.

A cylindrical casing 24, telescoping the casing l0, has suitably secured to its lower end a lpiston 26 reciprocable in the casing I0. The piston has a concentric orifice 28 for cooperation with the metering pin I6 and a plurality of spaced ports l30 controlled as by a flap valve 32 operative to is closed as by a diaphragm 34 secured against displacement by a welding bead 36. "I'he bead also serves to seal the upper end ofthe vcasing against leakage; and a filling lopening inthe wall of the casing adjacent the diaphragm 34 is nor- 'mally closed as by a plug 38.

The casing. andthe casing I0 are suitably securedtogether'. As shown, the casing 24 is .adapted to slide smoothly througha ring 40 seated on the annularshoulder 22 in Ythe packing chamber 20 an'd a collar 42 in the open end oi the packing chamber 20; Suitable packing material 44 is interposed between the ring 4l and the collar 42, and a retaining ring 48- threaded,

on the packing chamber serves to secure the as-y sembly against displacement.

The casing 24 has arranged in its wall just back of the had'ot the piston 26 a plurality oiports 48 providing communications .between the i casing l0 and the casing 24. When the strut is in extended position and the piston fully retracted, these communications are closed by the ring `411 in the packing chamber 20. Upon collapse ofthe strut and the resultant movement of the piston, as when landing, the ports 48 are un# covered. This establishes communication between the casings lll and 24, and results in materially increasing the area, and lowering toa marked degree the pressure in tbe strut. As the strut again resumes its extended position the iluid returns from the casing lil through the ports 48 into the casing 24.

' Suitable means for resiliently supporting the load after the initial shock oi. landing has been valve, not shown, and suitably attached to the other end of the casing A54 is a collar 62 having an inturned flange fthe purpose of which will hereinafter appear.

An annular piston 66 reciprocable on the cash ing 24 within the chamber has on its head a leak-proof cup 68 for inhibiting seepage of air from the cylinder 58 past the piston. A 'sleeve' 'lll telescoping the casing 24 has one of its ends secured to the annular piston andvtheother end of the sleeve 10 is provided with an inturned flange 12 adapted to engage the collar 42 upon collapse of the Ystrut but only after the initial shock of landing has been absorbed. The piston 68 also has secured to its backl a exible ring 14 adapted to seat cn the retaining ring 64 when the piston is in fully retracted position.

` Assuming that the strut is iilled with suitable fluid up to a level slightly above the piston 28, that the remaining portion of the strut is iilled with air under light pressure or at latmospheric pressure, and that the chamber 58 is lled with air or gas under high pressure, under these condltions, the strut under impact of landing causes the nuid in the casing Il to'actuate the valve so as to close 'the ports. 88, and thereafter `the iluid is forced through the orifice -28 in the head of the 24. mresmtsm effectively damping the initial my application-No1, 143,456, med May 19, 1937,

patented April 16, 1940, as Patent No. 2,197,474.

shock of landing. During this operation the fluid flows from the casing 2l through the ports Il into the casing Il 'back of the piston 26, resulting in the shock of landing, the iiange 12 of the sleeve 'Il engages the collar I2 and transfers a portion oi the load to the piston 66 attached togl the sleeve 1U. Movementpf the piston 6B is resisted by the pressure on the air or gas in the chamber 56. Accordingly. the load is resiliently supported when the airplane settles on the ground and when the airplane is taxying.

When the plane takes of! or ascends, the strut returns -torits fully extended position. As the plane ascends, air or gas under pressure inthe chamber 5I returns the annular piston 66 to its extended position, and as the piston returns to its extended position torce is transmitted therefrom through the sleeve I to the casing Il, resulting in movement oi the casing I0 corresponding to the4 movement of the piston I6. Further movement of the casing Il to its fully extended position results from the pressure on the liquid in the strut, the weight of the casing II and the landing gear attached thereto, and as the strut asslnnes its fully extended position the iluid in tle casing back of the piston 2B is returned there- 2l asfrom through the ports Il to the the uuid in the struc settles '1:01a iev slightly .abovethepistom Y While one embodiment has been described 'in detail, it is not 'my intention to limitthe scope of the invention to that particular embodiment, or otherwise than by the terms of the appended claims. The present application is a division of I claim: e 1. A shock strut Vhaving telescoping tubes of different diameters, 'a short tube coaxially surrounding and spaced from thelsmall'er of said tubes some distance from the end of the larger tube, means securing the short tube to the smaller of said tubes at the end opposite thel larger tube and for closing said end of. the short tube, a floating annular piston in the space between the short tube and said smaller tube, and means for causing the larger tube to operate the annular piston after a predetermined stroke of said telescoping tubes.

2. A shock strut having telescoping tubes of different diameters,A a short tube coaxially surrounding and spaced from the smaller of said tubes some distance from' the end oi the ,larger tube, means securing the short tube to the small- A*means aiiixed to the exterior of one of said telescoping members to yform an axially parallel chamber, a piston adapted to t said chamber,

and means exterior to both telescoping Vmem- :bers operable upon the telescoping of the members to cause said piston to traverse its chamber.

V CARL v. .I oHNsoN. 

